The present invention relates to optical connectors, and particularly to an optical connector subassembly comprising a ferrule and a base member
Optical fiber connectors are an essential part of substantially any optical fiber communication system. Optical fiber connectors generally have two functions, one being the maintenance of two optical fiber ends such that the core of one of the fibers is axially aligned with the core of the other fiber to allow substantially all of the light from one fiber to be coupled into the other fiber. This is a particularly challenging task because the light-carrying region (core) of an optical fiber is very small. The other function of an optical connector is to provide mechanical stability and protection to the junction in its working environment. Achieving low insertion loss in the coupling of two fibers is generally a function of the alignment of the fiber ends, the width of the gap between the ends, and the optical surface condition of either or both ends. Stability and junction protection is generally a function of connector design, for example, minimization of the different thermal expansion and mechanical movement effects.
A variety of connector plugs are known in the art. For a discussion of optical fiber connectors, see, for example, Optical Fiber Telecommunication, S. E. Miller and A. G. Chynoweth, editors, Academic Press (1988), especially pp.301-325. One of the known connector plugs is shown in U.S. Pat. No. 4,934,785. The connector plug comprises a ferrule, a base member which holds the ferrule, a compression spring, and a cap that surrounds the ferrule and the spring. The ferrule is held rigidly in the base member by an adhesive. The ferrule and the base member each include an opening that extends lengthwise from one end to the other. For clarity, each opening will be referred to as a xe2x80x9cpassagewayxe2x80x9d when discussing the ferrule, and a xe2x80x9cborexe2x80x9d when discussing the base member. The central axis of the passageway and the bore need to be axially alignedxe2x80x94particularly in the region where the ferrule meets the base member so that an optical fiber can be threaded along their common axis. And while manufacturing tolerances may approach xe2x80x9czeroxe2x80x9d, practical considerations such as cost have dictated that axial alignment tolerance be relaxed while still assuring that an optical fiber can pass through the junction where the bore of the base member meets the passageway of the ferrule. Heretofore, this concern has been handled by designing a fiber entry funnel in the proximal end of the ferrule where the fiber is inserted. Such a funnel can be produced in a variety of different ways such as by grinding, etching, or fire polishing. However, this is a process that consumes time and resources and ultimately leads to a product having a higher final cost.
In addition, the method of joining the ferrule with the base member by an adhesive has the following drawbacks. First, the adhesive can frequently enter the funnel and then block the entry of the optical fiber during the adhesive process. Secondly, the ferrule will become separated from the base member if the adhesive loses effectiveness over time. Furthermore, the joining method is costly and time-consuming.
Therefore, an improved optical connector subassembly having a ferrule and a base member that overcomes the above-mentioned disadvantages is desired.
A main object of the present invention is to provide an optical subassembly which has a ferrule and a base member which are joined firmly together and which have their central axes accurately axially aligned.
Another object of the present invention is to provide a cheap optical subassembly which is manufactured easily and efficiently.
To achieve the above objects, an optical connector subassembly comprises a ferrule, a base member and a locking element. The ferrule defines an axial passageway for receiving a core of an optical cable, and a plurality of holes provided in an outer surface of the ferrule. The base member has a receiving space for receiving a lower portion of the ferrule, a bore that is formed along a central axis of the base member and ends in a funnel for guiding an optical fiber into the passageway, and a plurality of openings formed in an upper portion of the base member corresponding to the holes of the ferrule and communicating with the receiving space. The locking element has a plurality of free extension portions that extend through the corresponding openings in the base member and into the corresponding holes of the ferrule to join the ferrule and the base member together.
Other objects, advantages and novel features of the invention will become more apparent from the following detailed description of a preferred embodiment thereof when taken in conjunction with the accompanying drawings, wherein: